Known integrated circuits (IC) for such receiver circuits, especially remote control receivers, such as, for example, the U2548 from Temic Semiconductor GmbH, have larger dimensions due to their technology, and therefore have a small interference coupling. Their size amounts to approximately 1.8 mm2. On the useful surface, these circuits comprise connection devices for the input signal, the output signal, the supply voltage, the ground connection and several adjusting or tuning devices. The functional operation of such a circuit consists in that the signal received from a photodetector, generally a photodiode—the received signal—is fed into an input circuit. The input circuit comprises a transimpedance amplifier, which amplifies pulsing input current signals and transforms them into voltage signals. These voltage signals are then processed in a signal preparation or processing device. The signal processing device comprises a regulating amplifier, a limiter, and a bandpass filter. In this context, the purpose of the regulating amplifier is to amplify the output voltage of the transimpedance amplifier according to the prescribed regulation. The limiter has the purpose of limiting the signal level swing or range, in order to avoid overdriving the bandpass filter. The bandpass filter enables the selectivity of the receiver and limits its bandwidth. The signals at the output of the bandpass filter are evaluated in a demodulator as an evaluating circuit. This demodulator consists of comparators, an integrator and a Schmitt trigger, and generates a switching signal for a driving transistor functioning as a switch, whereby a digital control signal is provided, for example to a microcontroller for further processing.
This known circuit further includes an amplification regulation, by means of which the amplification of the receiver is regulated or adjusted to correspond to an interference field, whereby a high sensitivity for the received signals is achieved, while nonetheless simultaneously, interfering influences, which may for example arise due to extraneous light, are suppressed to a great extent, so that hereby as far as possible no output pulses are generated by the driving transistor.
This known circuit, however, has the disadvantage, that its circuit surface area is reduced through the application of new technologies, whereby, due to switching processes in the output portion of the receiver, especially through the driving transistor, interferences or disturbances are caused, for example in the form of oscillator oscillations due to the capacitive couplings and ground potential reduction that are now effective within the circuit, whereby these interferences or disturbances cannot be removed by the amplification regulation.
To solve such problems, it is known from a Toshiba Data Sheet regarding the monolithic integrated photo circuit TPS831, to connect an external capacitor of the size 1000 pF between the output terminal or connection V0 and ground terminal or connection GND, in order to prevent oscillations—as it is termed therein. The evident disadvantage of this solution is that additional costs are caused in addition to the chip costs, due to the additional component, and that the demodulated output pulse is corrupted or falsified through this capacitor.